Low-metallicity massive single stars with rotation III. Source of ionization and C IV emission in I Zw 18

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985815%3A_____%2F25%3A00643351" target="_blank" >RIV/67985815:_____/25:00643351 - isvavai.cz</a>

Alternative codes found

RIV/00216224:14310/25:00144630

Result on the web

<a href="https://hdl.handle.net/11104/0373288" target="_blank" >https://hdl.handle.net/11104/0373288</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1051/0004-6361/202452483" target="_blank" >10.1051/0004-6361/202452483</a>

Result language

angličtina

Original language name

Low-metallicity massive single stars with rotation III. Source of ionization and C IV emission in I Zw 18

Original language description

Context. Chemically homogeneously evolving stars have been proposed to account for several exotic phenomena, including gravitational-wave emissions, gamma-ray bursts and certain types of supernovae. Aims. Here we study whether these stars can explain the observations of the metal-poor star-forming dwarf galaxy, I Zwicky 18. Methods. We apply our synthetic spectral models from Paper II to (i) establish a classification sequence for these hot stars, (ii) predict the photonionizing flux and the strength of observable emission lines from a I Zw 18-like stellar population, and (iii) compare our predictions to all available observations of this galaxy. Results. Adding two new models computed with PoWR, we report that (i) these stars follow a unique sequence of classes: O> WN> WO (i.e. without ever being WC). From our population synthesis with standard assumptions, we predict that (ii) the source of the UV C IV lambda 1550 Å and other emission bumps is a couple of dozen WO-type Wolf-Rayet stars (not WC as previously assumed) which are the result of chemically homogeneous evolution, while these, combined with the rest of the O-star population, account for the high He II ionizing flux and the spectral hardness. Contrasting our results against published optical and UV data from the literature and accounting for different aperture sizes and spatial regions probed by the observations, we find that (iii) our models are highly consistent with existing measurements. Conclusions. Since our massive Pop II stars might just as well exist in early star-forming regions, our findings have implications for upcoming James Webb Space Telescope (JWST) surveys: the first galaxies in the high-redshift Universe may also experience the extra contribution of UV photons and the kinds of exotic explosions that chemically homogeneous stellar evolution predicts. Given that our results apply for binary populations too as long as the same fraction (10%) of the systems evolves chemically homogeneously, we conclude that the stellar progenitors of gravitational waves may very well exist today in I Zw 18.

Czech name

—

Czech description

—

Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10308 - Astronomy (including astrophysics,space science)

Project

<a href="/en/project/GA25-15910S" target="_blank" >GA25-15910S: Hot star winds: solving uncertainties of mass loss near the Eddington limit</a><br>

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2025

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Astronomy & Astrophysics

ISSN

0004-6361

e-ISSN

1432-0746

Volume of the periodical

703

Issue of the periodical within the volume

Nov.

Country of publishing house

FR - FRANCE

Number of pages

18

Pages from-to

A131

UT code for WoS article

001616252400004

EID of the result in the Scopus database

2-s2.0-105021945501